Field of the Invention
The present invention relates to a hybrid-type wheel loader.
Background Information
Recently, a hybrid-type wheel loader has been proposed that travels using driving power from an engine and driving power from a motor. A hydraulic-mechanical transmission (HMT) or an electric-mechanical transmission (EMT) are disclosed as transmissions for a hybrid-type wheel loader as in, for example, Japanese Patent Laid-open No. 2006-329244.
The HMT has a planetary gear mechanism, and at least two hydraulic motors connected to rotating elements of the planetary gear mechanism. The hydraulic motor functions as either a motor or a pump in response to the travel state of the wheel loader. The HMT is configured to enable stepless changing of the rotation speed of the output shaft by changing the rotation speed of the hydraulic motor.
An electric motor may be used in an EMT in place of the hydraulic motor in the HMT. The electric motor functions as either a motor or a generator in response to the travel state of the wheel loader. Similar to the HMT, the EMT is configured to enable stepless changing of the rotation speed of the output shaft by changing the rotation speed of the electric motor.